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Useful Information
Ultimately the enclosure you build determines the performance
of your subwoofer. The size and port tuning frequency of a
ported box determines the low-frequency extension and output
of the subwoofer. This ARC Audio subwoofer is designed to
performs well when used in both sealed and ported enclosures.
The acoustics of your vehicle influence bass response. The
small interior size of most cars and trucks boosts low
frequencies dramatically. A smaller enclosure then normal may
be needed to achieve a flat bass response. As a rule, below
50Hz (depending on cabin size), bass response increases at
about 12dB per octave as the frequency decreases. This "Cabin
Gain" adds significant bass output to the subwoofer system.
Recommendations are included in this manual for both sealed
and ported enclosure types. The sealed enclosure design will,
in most cases, give you the best sound quality and take up less
space in your vehicle. The ported box design will offer more
output then the sealed enclosure (about 3 - 4 dB more), but it
will reduce the power handling and require more space to
install. The recommended ported enclosure is not designed for
“competition SPL” performance, it is designed for normal
listening. It will increase the low frequencies output and
increase the overall volume while still sounding good when
properly tuned and installed.
A Note About Power Handling
ARC Audio woofers are designed to perform for years without
any problems. The RMS power noted under the specifications
is the recommended continuous power for long term use. All
woofers generate heat. It is possible to dissipate only so much
of this heat. The woofer can handle as much as twice its rated
RMS power for short periods. This is the MAX power rating.
Continued use of this woofer at greater then the RMS power
rating will result a damaged (burnt) voice coil. This damage is
considered abuse and is NOT covered under the warranty.
Small Amp Myth
Under powering a woofer is fine. This woofer will suffer no
damage from a 100 watt amp if it is correctly tuned. However,
even a small amp that is being over driven (clipped) can destroy
a sub. Use your power wisely. Clipping can be heard as a dull
thud or a popping sound. If you hear any change in the tone of
your subwoofer this is a danger sign. TURN IT DOWN. If you
want more volume get a bigger amp or add another woofer.
Physics
"Energy cannot be created or destroyed, only change forms".
What does this mean? Your amp does not make power, it takes
power from your battery and converts it into a different form.
The subwoofer is just another kind of converter. It changes AC
voltage from the amp into changes in air pressure (that's all
sound is) and HEAT. The more energy being converted the
more heat. A speaker can not reproduce DC voltage (produced
when an amp clips) but this energy must go somewhere. It is all
converted into heat. This is why clipping is so dangerous to a
speaker.
A great deal of energy can also be lost in the enclosure. If your
box is not strong enough the sides will flex. It takes energy to
flex the box. This energy is not being converted into sound. In
short, the stronger the box the less energy will be lost.
So build it strong.
This same thing can happen to the car body. Sound deaden, it
will sound better and hit harder.
Building an Enclosure
It is recommended that you use 3/4" MDF (Medium Density
Fiberboard) to build an enclosure. Glue all your joints with
yellow glue and secure then with screws or nails.
Make sure the enclosure will fit and that you have adequate
room to get it in and out of the vehicle.
Calculating Enclosure Volume
It is difficult to give exact box dimensions that are universal
for all cars and trucks. It is for this reason that you must be
able to calculate the space in which you have available in
order to achieve the proper air volume required.
Calculating External Volume
1) To calculate box volume, measure the outside Width x
Height x Depth of the enclosure.
Example 12" x 14" x 9" = 1512 cubic inches.
2) Next convert cubic inches into cubic feet. To do this, you
must divide the cubic inch total by 1728 .
Example 1512 cu in
÷
1728 = .875 Cubic feet.
Calculating Internal Volume
1) To calculate the internal (net) volume of the above box
first multiply the thickness of the wood you are using by Two
(2).
Example: ¾" x 2 = 1 1/2"
2) Next subtract 1.5" from each of the outside measurements
of the box. Width 12" -1.5" = 10.5" . Height 14" -1.5" = 12.5" .
Depth 9" -1.5" = 7.5"
3) Multiply the new totals (H x W x D)
Example: 10.5" x 12.5" x 7.5" = 984.375 cubic inches.
4) Now convert cubic inches into cubic feet. To do this, you
divide the cubic inch total by 1728.
Example 984.375
÷
1728 = .5696 cubic feet.
For additional information call ARC Audio Tech support at:
209-543-8706
USEFUL INFORMATION